Vehicle radar sensor assembly

ABSTRACT

A radar electronics module includes a support structure having a first surface having a plurality of recesses with a transmitter circuit board and a receiver circuit board disposed thereon. The transmitter and receiver circuit boards are disposed over the first surface of the supports structure such that transmitter and receive circuits are disposed in cavities on the support structure. The radar electronics module further includes a digital/power supply circuit printed wiring board (PWB) disposed on a second surface of the support structure and a connector disposed on the support structure. The connector is disposed in such a way that it provides electrical connections for at least one of power signals, analog signals or digital signals between at least two of the digital/power supply PWB, the transmitter circuit board and the receiver circuit board.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation application of U.S. patentapplication Ser. No. 11/323,816 entitled “Vehicle Radar SensorAssembly,” filed on Dec. 30, 2005; now U.S. Pat. No. 7,603,097 which isa continuation-in-part of U.S. patent application Ser. No. 11/027,523filed on Dec. 30, 2004 now U.S. Pat. No. 7,680,464.

FIELD OF THE INVENTION

This invention relates generally to housings for radio frequency (RF)systems and more particularly to structures and techniques supportingradar structure and circuits.

BACKGROUND OF THE INVENTION

As is known in the art, in some applications it is necessary to coupleradio frequency (RF) signals between multiple printed wiring boards(PWBs). Such connections are often made by using either a coaxial cableor a printed shielded RF conductor circuit (also referred to as a flexcircuit). Both of these techniques are troubled by implementationcomplexity, reliability concerns, as well as cost issues.

A coaxial cable connection typically requires the mounting of aconnecting pin on the PWB. The coaxial cable shield is stripped toexpose a section of a center conductor which is then soldered to theconnecting pin. This is done through a cover assembly, which istypically provided as a two-piece assembly, to provide a required levelof isolation between different circuit portions. Although this type ofconnection results in a relatively high level of performance, it is arelatively complicated assembly requiring precision parts.

A multi-layer flex circuit PWB interconnection can be implemented bysoldering a center conductor from a flex-print circuit to a signal pathon a PWB. Although this approach has fewer parts, the flex-print circuitis relatively expensive because of the need to include ground planes andvia holes to achieve desired isolation levels. Furthermore, it isrelatively difficult to obtain a good electrical seal around a flexcircuit and this makes it difficult to achieve a desired level ofisolation between the PWBs being connected through the flex circuit.More, in high frequency applications, the losses through this type ofstructure can be relatively high.

SUMMARY OF THE INVENTION

In accordance with the present invention, a radar electronics moduleincludes a support structure having a first surface having a pluralityof recesses provided therein. A radio frequency (RF) transmitter circuitboard and an RF receiver circuit board are disposed over the firstsurface of the support structure such that RF circuits on the respectivetransmitter and receiver circuit boards are disposed in respective onesof the recesses provided in the support structure. The transmitter andreceiver circuits are provided having conductive regions providedthereon such that when the transmitter and receiver circuit boards aredisposed over the recesses in the support structure, the recesses formelectrically sealed cavities. The radar electronics module furtherincludes a digital/power supply circuit printed wiring board (PWB)disposed on a second surface of the support structure opposite the RFtransmitter and receiver circuit boards. A connector (also referred toas a header) is disposed on the support structure in such a way that theconnector provides electrical connections for at least one of powersignals, analog signals or digital signals between at least two of: thedigital/power supply PWB, the transmitter circuit board and the receivercircuit board.

With this particular arrangement, a compact radar electronics moduleappropriate for use as part of a vehicle radar system is provided. Thesupport structure provides a frame for mounting radar transmitter andreceiver circuits in close proximity to each other without interferingwith each other either physically or electrically. The transmittercircuit board includes a transmitter circuit and a transmit antenna andthe receiver circuit board includes a receiver circuit and a receiveantenna. The configuration of the support structure allows the transmitand receive antennas (and related transmit and receive circuits) to bothbe mounted on the same side of the support structure while at the sametime physically separating the two antennas without adding additionalhardware and cost. The transmitter and receiver circuit boards areprovided having certain conductive regions shaped such that when thetransmitter and receiver circuit boards are disposed over the supportstructure (thereby covering recesses in the support structure), therecesses become cavity structures having disposed therein RF circuitsand components. The cavity structures serve to isolate transmitter andreceiver circuitry existing in close proximity to each other on thetransmitter and receiver circuit boards. Disposing the RF circuits andcomponents in metal cavities serves to further electrically isolate theRF circuits and components from each other thereby reducing the amountof undesired RF leakage signals and cross-talk between the RF circuitsand components. Placing the RF circuits and components in the cavitiesalso removes the need to apply a conformal coating over the circuitboards and the RF circuits and components which is desirable sinceconformal coatings typically cause additional attenuation in RF signalspropagating in RF circuits and components. Thus, the support structure(including the recesses provided in the support structure) bothphysically and electrically separates the transmitter and receivercircuit boards as well as electrical circuits on the transmitter andreceiver circuit boards. Also, disposing RF circuits and components inmetal cavities helps shield and thus protect them from environmentalfactors (e.g. rain) The support structure also includes as an integralpart thereof, at least a portion of a waveguide transmission line whichcouples RF signals between the transmit and receive circuit boards. Inone embodiment, a portion of a support structure has three sides of arectangular transmission line integrally formed therein. A fourth wallof the waveguide transmission line, is provided by a conductor which canbe provided as a printed circuit conductor disposed on either thedigital/power supply PWB or the transmitter or receiver circuit boards(depending upon circuit configurations which may be different fordifferent applications). Thus, when the circuit board is disposed overthe support structure, the conductor on the circuit board forms thefourth waveguide wall. Also, the surface of the support structure isprovided having no holes or openings therein which would allow RFsignals to pass from one side of the support structure to the other sideonce the digital/power supply circuit PWB and transmitter and receivercircuit boards are mounted thereon. Thus, the support structure alsoacts as an RF shield between the digital/power supply circuit PWB andthe transmitter and receiver circuit boards. That is, by mounting thedigital/power supply circuit PWB on a side of the support structureopposite the transmitter and receiver circuit boards, the supportstructure electrically isolates the digital/power supply circuit PWBfrom RF signals generated by circuitry on the transmitter and receivercircuit boards. Thus, the digital/power supply circuit PWB is isolatedfrom stray RF signals (e.g. leakage and other signals) emanating fromthe transmitter and receiver circuit boards. The connector provides ameans for coupling desired signals between the transmitter circuitboard, the receiver circuit board and/or the digital/power supplycircuit PWB. Thus, the support structure provides a single integratedstructure which physically organizes, and electrically isolates radarelectronics disposed on the digital/power supply circuit PWB, and thetransmitter and receiver circuit boards. Also, the support structureacts as a heat sink and helps dissipate thermal energy generated bycircuits on the digital/power supply circuit PWB and the transmitter andreceiver circuit boards. The support structure can be manufactured usingrelatively low cost materials and low cost manufacturing techniques.Thus, the support structure is a single, low cost, integrated structurewhich serves multiple functions including but not limited to: physicalseparation and electrical isolation of transmitter circuits, receivercircuits, digital circuits and power circuits (including isolationbetween transmit and receive antennas); ease of electricalinterconnection between transmitter circuits, receiver circuits, digitalcircuits and power circuits (including DC power connections and RFsignal connections) through a connector and/or an integral waveguide;thermal dissipation of heat generated by electronics on all of thecircuit boards mounted thereon; and, importantly, integrates all of theantenna connections (transmit and receive antenna connections) in asingle support structure.

In accordance with a further aspect of the present invention, a sensorassembly includes a housing, an electrical shield disposed in thehousing and a radar electronics module disposed in the housing over theelectrical shield.

With this particular arrangement, a compact sensor assembly which isprotected from environmental factors and which is provided from a smallnumber of parts is provided. In a preferred embodiment, the radarelectronics module is provided from a support structure having adigital/power supply circuit PWB mounted on one side thereof andtransmitter and receiver circuit boards mounted on a second, oppositeside thereof. The shield is provided having no openings provided in thebottom surface thereof and is provided having a sized and shape whichsubstantially matches a shape and size of a bottom surface of thehousing and a side of the support structure on which the digital/powersupply circuit PWB is disposed. Since the shield is a closed surface(i.e. no openings), when it is disposed over the digital/power supplycircuit PWB of the radar electronics module, the shield essentiallyseals one side of the radar electronics module. The transmitter andreceiver circuit boards may be provided from a material which canwithstand environmental conditions and are provided having transmitterand receiver electronic components disposed only on one side thereof.The transmitter and receiver circuit boards are mounted to the supportstructure in such a way that any transmitter and receiver electroniccomponents are disposed in closed cavities formed on the supportstructure by mounting the transmitter and receiver circuit boards on thesupport structure. Thus, once the transmitter and receiver circuitboards are mounted to one side of the support structure (e.g. usingconductive epoxy) and the shield is disposed over the second side of thesupport structure (i.e. over the digital/power supply circuit PWB) theradar electronics module corresponds to a substantially sealed unitwhich is disposed in the housing. In one embodiment, the housing isprovided as an open box with the transmit and receive antennas facingthe open side of the housing. A radome can be disposed over the openportion of housing and coupled to the housing any one a variety ofdifferent techniques including but not limited to laser welding theradome to the housing. In this case, the sensor assembly is providedhaving a so-called box-within-a-box packaging structure. That is, theradar electronics module with the shield disposed over one side thereofforms a first closed box and the housing having the radome coupledthereto forms a second closed box. By placing the radar electronicsmodule/shield (i.e. the first box) inside the housing/radome assembly(i.e. the second box) the sensor assembly is provided having abox-within-a-box packaging structure. In this manner, the circuitcomponents are shielded (i.e. protected) from the environment by twosets of barriers or walls. The first set of walls being provided by thecombination of the radar electronics module and shield (i.e. the firstbox) and the second set of walls being provided by the housing/radomeassembly (i.e. the second box). The first set of walls which protect theRF circuit components correspond to the walls of the cavities formed bythe arranging the transmitter and receiver circuit boards over therecesses in the support structure. The first set of walls which protectthe circuit components on the digital/power supply circuit PWBcorrespond to the walls provided by the shield disposed over thedigital/power supply circuit PWB.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing features of this invention, as well as the inventionitself, may be more fully understood from the following description ofthe drawings in which:

FIG. 1 is an isometric view of two printed wiring boards (PWBs) having awaveguide radio frequency (RF) interconnect therebetween;

FIG. 1A is a cross-sectional view of a the RF interconnect shown in FIG.1 taken across lines 1A-1A in FIG. 1;

FIG. 2 is an isometric view of a waveguide RF interconnect having atuning structure;

FIG. 2A is an isometric view of the waveguide RF interconnect of FIG. 2with the waveguide shown in phantom;

FIG. 3 is an isometric top view of a PWB support frame having anintegral waveguide;

FIG. 3A is an isometric bottom view of the PWB support frame shown inFIG. 3;

FIG. 3B is an enlarged view of the integral waveguide shown in FIG. 3;

FIG. 3C is an enlarged view of the waveguide opening apertures shown inFIG. 3A;

FIG. 3D is a cross-sectional view of the integral waveguide on the PWBsupport frame taken across lines 3D-3D of FIG. 3B;

FIG. 3E is an enlarged view of a portion of the waveguide taken acrosslines 3E-3E of FIG. 3D;

FIG. 4 is an isometric view of two RF PWBs mounted to a PWB supportframe;

FIG. 5 is a cross-sectional side view of a pin feed for a waveguide RFinterconnect coupled to a PWB;

FIG. 6 is a cross-sectional side view of an edge launch waveguidecoupled to a PWB;

FIG. 7 is a is a cross-sectional side view of a PWB RF interconnect;

FIG. 7A is an isometric view of a portion of the PWB RF interconnectshown in FIG. 7;

FIG. 7B is a cross-sectional view of a portion of the PWB RFinterconnect shown in FIG. 7;

FIG. 8 is an exploded view of a sensor assembly;

FIG. 9 is an isometric view of a radar electronics module;

FIG. 10 is an isometric view of a support structure having a connectorand transmitter and receiver circuit boards coupled thereto; and

FIG. 11 is an isometric, cut-away view of a portion of a radarelectronics module.

DETAILED DESCRIPTION

Referring now to FIGS. 1 and 1A in which like elements are providedhaving like reference designations, an RF interconnection 10 betweenfirst and second radio frequency (RF) Printed Wiring Boards (PWBs) 12,14 (also sometimes referred to as printed circuit boards or PCBs)includes a waveguide transmission line 16 having first and second ends16 a, 16 b (also referred to as waveguide port apertures or more simplywaveguide ports) and pair of waveguide feed circuits 18, 20 disposed tolaunch signals into and couple signals out of the transmission line 16at ends 16 a, 16 b, respectively.

The feed circuits 18, 20 are each provided as an integral part of atleast a portion of the PWBs 12, 14 respectively. In the exemplaryembodiment shown in FIGS. 1 and 1A, the feed circuits 18, 20 areprovided as radiating elements and in particular are provided asmicro-strip (or so-called “patch”) antenna elements on PWB surfaces 12a, 14 a. Each patch is provided from a conductive region 22 a, 22 bseparated from PWB ground planes 13, 15 by dielectric regions 24, 26.

Each end 16 a, 16 b of the waveguide 16 must be conductively attached tothe ground planes 13, 15 of the respective PWBs 12, 14. The waveguide 16can be attached to the PWBs via a conductive epoxy, via a solderconnection, via a pressure contact or by any other means now or laterknown to those of ordinary skill in the art.

By using a waveguide section for the transmission line and incorporatingthe waveguide feeds into each PWB, an RF interconnect between two PWBswhich is reliable and cost-effective is provided. Since the waveguidefeeds 18, 20 are incorporated into each PWB, separate connectingstructures are not needed on each of the PWB's and the RF interconnectis provided having fewer parts than other RF interconnect techniques.Moreover, as will become evident from the description providedhereinbelow, since the waveguide 16 can be constructed in many differentways, the waveguide could easily be incorporated into a PWB supportstructure or package, essentially reducing the part count of the RFinterconnect to zero.

The particular size, shape, transmission and other characteristics ofthe waveguide will depend upon a variety of factors including but notlimited to the frequency of operation and the type of PWB's beingconnected. For example, the size of the waveguide opening could bedifferent for each PWB due to differences in dielectric constants of thePWB materials; the waveguide may be filled with dielectric to reduce thesize for lower frequency operation or and the waveguide can be providedas so-called ridged waveguide for use in relatively broad bandapplications.

Likewise, the particular type of feed to use in any application willdepend upon a variety of factors including but not limited to the PWBtype and construction as well as the frequency band in which the feedmust operate and the bandwidth requirements. While the exemplaryembodiment, of FIGS. 1 and 1A illustrate the feed structure as amicrostrip antenna element, in other embodiments, it may be desirable ornecessary to provide the feed structure as a stacked patch antennaelement (e.g. if an application requires a relatively wide frequencybandwidth). A stacked patch can be provided, for example, byincorporating the stacked patch feed in the PWB design or by adding intothe waveguide a foam insert having a parasitic patch on one side thereofand arranging the insert above a patch on the PWB (such as patch 22 a)to provide a stacked patch structure.

It should be appreciated that any radiator design may be used as a feedfor the waveguide structure. The feed (particularly when provided as aprinted circuit radiator) may be provided having any desired shapeincluding but not limited to a rectangular shape, a square shape, anoval shape, a round shape, a cross shape a polygonal shape or even anirregular shape. The particular type and shape of the feed will beselected in accordance the needs of the particular application and inaccordance with a variety of factors including but not limited to thetype of transmission line being used, the size and shape of thetransmission line and the amount of space available on the PWB for thefeed.

Referring now to FIGS. 2 and 2A in which like elements are providedhaving like reference designations, an RF interconnection 30 includes awaveguide transmission line portion 32 (or more simply a “waveguide 32”)and associated feed structures 34, 36 (visible in FIG. 2A) through whichRF signals are coupled between a pair of PWBs 38, 40 (only portions ofthe PWBs 38, 40 being shown in FIGS. 2 and 2A for clarity). Thewaveguide transmission line portion 32 and associated feed structures34, 36 (FIG. 2A) may be similar to the RF interconnection and associatedfeed structures described above in conjunction with FIGS. 1 and 1A.

The waveguide is provided having a tuning structure 42 disposed in awall thereof. The tuning structure 42 is selected having a size andshape which improves the impedance match between the waveguide ports andthe feed structures. In the exemplary embodiment of FIG. 2, the tuningstructure 42 is provided as a notch 42 in a sidewall of the waveguide32. The particular size, shape and location of the notch can bedetermined using empirical techniques to provide a desired impedancematch between the waveguide 32 and the feed structures 34, 36 on thePWBs 38, 40.

It should be appreciated that the PWBs 38, 40 may be provided fromdifferent materials. For example, PWBs 38, 40 may be provided frommaterials having different electrical properties such as relativedielectric constants, and also having different structuralcharacteristics such as board thicknesses. In one embodiment, one PWB isprovided from a so-called soft substrate material (e.g.polytetrafluoroethylene (PTFE)/woven glass or combinations thereof)having a relative dielectric constant of about 3.02 while the other PWBis provided from a so-called thick film substrate (e.g. low temperatureco-fired ceramic—LTCC) having a relative dielectric constant of about7.4.

This difference in PWB characteristics results in a different waveguideopening for each PWB which results in an inherent mismatch within thewaveguide. Thus, to compensate for this mismatch between the openings,the waveguide is provided having a tuning structure 42.

Although the tuning structure 42 is here shown as a single protrusion orpost in a single waveguide wall, other types of tuning structures mayalso be used to “tune” or provide a desired impedance match between thewaveguide and one or both of the feed structures. For example, multipleposts, openings, broadwall curtains, narrow wall curtains, steps or anycombination thereof may be provided in one or more internal surfaces ofthe waveguide walls. Alternatively, conductive elements (e.g. probes) ordielectric elements may be inserted into the waveguide. Alternativelystill, one or more tuning elements may be provided as part of the PWBs38, 40 (e.g. tuning circuits may be printed, etched or otherwiseprovided on one or both of the PWBs. It should also be appreciated thatmore than one tuning structure may be used. For example, separate tuningstructures may be provided on the waveguide to match each waveguide portto the field structure.

Thus, it should be appreciated that the RF interconnect can be modifiedto accommodate any type or combination of PWB interconnection and anysuch modifications are considered to be within the scope of what iscovered by the claims.

Referring now to FIG. 2A, the waveguide is shown in phantom to revealthe feed structures 34, 36. As can be seen, the feed structures are eachprovided as integral portions of the PWBs' 38, 40 and in particular, thefeed structures are provided as patch radiators disposed in thewaveguide apertures. The patch radiators couple signals to and from thewaveguide through the apertures.

Strip transmission lines 44, 46 couple RF signals between the patchradiators and other circuits (since only a portion of each of the PWBs38, 40 are shown in FIG. 2A, no other circuits are visible in FIG. 2A).A plurality of via holes generally denoted 48 are disposed about each ofthe patch radiators to provide a cavity for the patch and a barrier toany leakage signals from the feed structures 34, 36.

It should be appreciated that the waveguide structures described abovein conjunction with FIGS. 1-2A are stand alone structures and areseparate from the PCBs themselves. The feed circuits (e.g. feed circuits22 a, 22 b in FIGS. 1 and 1A), however are provided as integral parts ofthe PCBs.

Referring now to FIGS. 3-3E, in which like elements are provided havinglike reference designations throughout the several views, a PWB frame 50adapted to hold one or more PWBs is provided having first and secondopposing sides 50 a, 50 b (FIG. 3A). Wall regions 52 project from asurface of side 50 a and form a bottom wall 53 a (FIG. 3B), sidewalls 53b (FIG. 3B), endwalls 53 c (FIG. 3B) and first and second openings 54 a,54 b which lead to waveguide port apertures 56 a, 56 b (FIG. 3C) of awaveguide 53. It should be appreciated that the waveguide 53 is notfully formed in the frame 50 as one side of the waveguide (in this casean E-plane wall opposite wall 53 a) is not formed as part of thewaveguide structure in the frame 50 as doing so would complicate theframe fabrication process. The waveguide wall could, however, beprovided as a separate piece part (e.g. a cover or plate) which iscoupled to the remaining waveguide portions by bonding, press-in,solder, welding, or any other technique well known to those of ordinaryskill in the art.

As can be most clearly seen in FIG. 3C, the first and second waveguideport apertures 56 a, 56 b of the waveguide portion 53 of the frame areexposed on a surface of a second side 50 b of the PWB frame 50 at firstand second ends of the waveguide portion 52.

The frame 50 may be provided from any suitable material including butnot limited to metal, plastic, or any other material suitable to supportPWB's disposed on the frame. In the case where the frame is providedfrom a nonconductive material, those portions of the frame correspondingthe internal waveguide walls must be coated or otherwise provided with aconductive layer or material.

The frame 50 can be fabricated using molding or any other fabricationtechniques known to those of ordinary skill in the art and with whichthe waveguide 53 can be provided as an integral part of the frame 50.That is, ideally, the waveguide 53 is provided in the frame without theuse of additional parts or additional assembly steps.

It should be appreciated that in this particular embodiment, thewaveguide openings 54 a, 54 b and apertures 56 a, 56 b are neither thesame size nor the same shape. Although the openings 54 a, 54 b may bethe same shape in some embodiments, in general, the size and shape ofeach waveguide opening 54 a, 54 b and aperture 56 a, 56 b is selected toprovide a suitable impedance match between the waveguide 53 and therespective feed circuits.

Two PWBs 70 a, 70 b shown in phantom in FIG. 3A, are disposed on side 50b of the PWB frame 50. The PWBs are provided having feed circuits 72 a,72 b (also shown in phantom in FIG. 3A) disposed on surfaces of the PWBsand located such that when the PWBs 70 a, 70 b are properly located onside 50 b of PWB 50, the feed circuits 72 a, 72 b are aligned with thewaveguide openings 54 a, 54 b to couple signals between the PWBs 70 a,70 b and the waveguide ports 54 a, 54 b. It should be appreciated thatany type of alignment or locating structure may be used to ensure thatthe PWBs 70 a, 70 b are properly aligned in the frame 50.

As shown in FIG. 3A, in this exemplary embodiment, a plurality ofalignment posts 60 a-60 e and alignment surfaces 60 f, 60 g project froma surface of side 50 b and are used to ensure proper alignment of thePWBs 70 a, 70 b on the PWB frame 50. In particular, sides 71 a, 71 b ofPWB 70 b are in contact with alignment posts 60 a-60 c. In this manner,feed circuit 72 b is properly aligned in the aperture 56 a

A pair of tooling holes 60 d, 60 e and surfaces 60 f, 60 g are used toalign PWB 70 a in the PWB frame to thus ensure that feed circuit 72 a isproperly aligned in the aperture 56 b. In particular, holes in the PWB70 a are aligned with the holes 60 d, 60 e and posts enter both the PWBholes and the PWB frame holes 60 d, 60 e to align the PWB 70 a on thePWB frame. The posts may project from the holes 60 d, 60 e or the PWBholes may be aligned with the holes 60 d, 60 e and the posts put inplace to maintain the alignment. It should be appreciated, of course,that other features could be added to the waveguide openings and PWBs toprovide alignment. In general any alignment technique known to those ofordinary skill in the art can be used to align the waveguide feed withthe waveguide opening.

The waveguide 53 is provided having a tuning structure 76 (FIG. 3B)formed as a part of the waveguide wall 53 b. In this particularembodiment, the tuning structure is provided as a post or protrusionwhich can be molded or otherwise provided as part of the sidewall 53 bduring a process for molding or otherwise providing the waveguide.

As shown in FIG. 3A, the waveguide is provided as an integral part ofthe PWB frame 50 and the feed structures 72 a, 72 b are provided as anintegral part of the PWBs 70 a, 70 b. Thus, the entire waveguide-PWBinterconnection is provided without the use of additional parts. Thatis, no parts separate from the frame 50 or PWBs 70 a, 70 b are requiredto provide the waveguide-PWB interconnection.

Referring now to FIG. 3D, an expanded cross-sectional view of theintegrated waveguide portion 53 of the PWB frame taken across lines3D-3D in FIG. 3B is shown. When the waveguide is molded as part of thePWB frame, the bottom wall 53 a, two sidewalls 53 b and two end walls 53c are formed. The top wall (i.e. the wall directly opposite the bottomwall 53 a) of the waveguide, however, is not formed since forming thetop wall would complicate the mold process. Rather, the top of thewaveguide is left open and a top must be placed over the walls 53 b, 53c to close the waveguide and thus make it a functional waveguidetransmission line.

To that end, a PWB 80 having a conductive region 82 provided thereon isdisposed over the open portion of the waveguide 53 and the conductiveregion 82 forms the fourth side of the waveguide 53. Other conductivetops not provided as part of a PWB may also be used to form the finalwaveguide wall.

Referring now to FIG. 3E, an expanded cross-sectional view of a portionof the integrated waveguide structure taken across lines 3D-3D in FIG.3D is shown. A channel 84 is formed in the waveguide wall. An inner wallportion 86 is provided having a height which is greater than an outerwall portion 88. A material 90 is disposed in the channel 80 to securethe conductive region 82 and/or provide a conductive seal between theconductive region 82 and the waveguide sidewalls 53 b and endwalls 53 c.The material 90 may be provided, for example, as a conductive epoxy 90.Other materials, including but not limited to conductive gaskets,conductive silicones, and crushable wire mesh may, of course, also beused. Alternatively still, the top wall of the waveguide may be providedhaving a knife-edge shape and a waveguide cover made of a materialsofter than the edge can be pressed or otherwise forced onto the knifeedge of the waveguide wall.

It should be appreciated that in FIG. 3E, a space (or gap) is shownbetween the conductive region 82 and a top surface of the wall 86. Thisspace is provided only for clarity in describing the drawings and toillustrate the shape of the conductive epoxy 90 shortly before theconductive region 82 is placed tightly against the top surface of thewall 86. In practice, no gap will exist between conductive surface 82and the top surface of the waveguide wall 86 against which the surfaceof the conductive region 82 is disposed.

The material 90 is placed in the channel 84 and when the conductiveportion of the cover is disposed over the waveguide, the cover pushesagainst and compresses the material 90. Since the inner wall 86 of thechannel wall 84 is higher than the outer wall 88 of the channel wall 84,any excess material flows to the outside of the waveguide rather thantoward the inside of the waveguide.

It should be appreciated that the waveguide portion can be constructedin many different ways. For example, it may be possible to form theintegral waveguide 53 in the frame 50 such that a side wall of thewaveguide (i.e. an H-plane wall in the waveguide) is omitted rather thanan E-plane wall. Alternatively, it may be desirable to form the integralwaveguide such that a split occurs down the center of an E-plane wall ofthe waveguide. This may be desirable since the concentration ofelectrical currents in that waveguide location are relatively weak (thisassumes, of course, a waveguide having a rectangular cross-sectionalshape and signals propagating within the waveguide in the dominant TEwaveguide mode). If other waveguide shapes or modes are used, then itmay be preferable to split the waveguide in a different location basedupon ease of manufacture and electrical performance characteristics.After reading the description provided herein, one of ordinary skill inthe art will understand how to select a waveguide configuration for aparticular application while incorporating the waveguide into the PWB orinto the PWB support package (i.e. PWB frame) in a manner whicheliminates the number of additional parts needed to provide PWBinterconnect (i.e. no additional parts needed to provide theinterconnect structure).

Referring now to FIG. 4, a pair of PWBs 100, 102 are disposed in a PWBframe 104. The PWB frame 104 has provided as an integral part thereof awaveguide structure 106 which forms a portion of an RF interconnectionthrough which RF signals can be coupled between the two RF PWB boards100, 102. It should be appreciated that to provide clarity in thedrawings and the written description, only portions of the PWBs 100,102, frame 104 and waveguide 106 are shown in FIG. 4.

A plurality of electrical components generally denoted 107 are disposedon the PWB 100. Each of the PWBs 100, 102 is provided having patchwaveguide feeds 108, 110. The feeds 108, 100 provide the excitation forthe waveguide structure at each PWB interface (i.e. where the waveguideapertures abut surfaces of the PWBs 100, 102). The patch feed circuits108, 110 are each provided as printed circuits on the PWBs 100, 102.Thus, the patch feed circuits 108, 110 are each provided as integralparts of the respective PWBs 100, 102.

It should be appreciated that in this exemplary embodiment, the two RFPWBs are of completely different construction. One PWB is provided froma so-called soft substrate material (e.g. polytetrafluoroethylene(PTFE), woven glass or combinations thereof) having a relativedielectric constant of about 3.02 while the other PWB is provided from aso-called thick film substrate (e.g. low temperature co-firedceramic—LTCC) having a relative dielectric constant of about 7.4.

This difference in PWB characteristics results in a different waveguideopening for each PWB which results in an inherent mismatch within thewaveguide. A protrusion 112 in the waveguide wall compensates for thismismatch between the openings. Thus, it should be appreciated that theRF interconnect can be modified to accommodate any type or combinationof PWB interconnection and any such modifications are considered to bewithin the scope of what is covered by the claims.

The RF interconnection is between the two RF PWB's 100, 102. A third PWB(not shown in FIG. 4) includes a printed conductive portion such thatwhen it is disposed on the PWB frame, the conductive portion of thethird PWB becomes the cover for the open portion of the waveguide. Thusthe waveguide cover can be provided as an integral part of a third PWB.Other types of covers which are not integral with a PWB, may of course,also be used and attached to the waveguide using any one of a variety oftechniques including but not limited to bonding, soldering, brazing,welding and press-in techniques.

The two RF PWB boards 100, 102 can be bonded to the support structure104, using conductive epoxy. Other fastening or attachment techniquesmay of course also be used. The attachment of the waveguide openings tothe PWBs 100, 102 is preferably included as part of the process ofbonding the PWBs to the frame.

As explained above, the cover for the waveguide may be provided as aconductive region on a third PWB and in this case, the cover can beattached in a similar fashion when the third PWB is similarly bonded tothe frame to complete the assembly. It should be appreciated that thethird PWB may be provided as a PWB on which digital circuitry isprovided. That is, the third PWB can be provided as a non-RF PWB.

Significantly, the interconnecting waveguide 106 is incorporated intothe design of the PWB support structure 104 and is not a separate part.Also, the waveguide cover and the waveguide feeds 108, 110 are allincluded as integral portions of the circuit layouts for each of threePWB's. Thus, the waveguide-PWB interconnect is provided without usingany additional parts. Furthermore, since the waveguide-PWB interconnectassembly process is included as part of the RF module assembly process,no process steps have been added to assemble the waveguideinterconnection. Thus, since the waveguide, covers, feeds, and assemblyare all included as part of an existing assembly and process, thisnormally troublesome and costly RF interconnection is realized withnearly no added cost.

Referring now to FIG. 5, an RF circuit includes a PWB 120 having awaveguide 122 disposed thereon. The waveguide is provided having a cover124. The waveguide 122 may be provided as an integral portion of a PWBframe. A feed 126 for the waveguide is provided using a launch pin 126.Thus, the structure of FIG. 5 may be similar the structure describedabove in conjunction with FIGS. 1-4 with the exception being that thefeed is provided from a pin 126 rather than as a printed circuit. Theadvantage to this design is that the feed design has a minimum impact onthe PWB design. However, the waveguide will take up more surface area onthe PWB in this configuration and there is the added cost of the pin andits assembly on the PWB.

Referring now to FIG. 6, an alternative waveguide configuration isshown. This configuration has an end launch feed 130 into a waveguide132 which is split (denoted as 133) along the E-wall (broad dimension)of the waveguide 132. The advantage of splitting the waveguide 132 thisway is that it reduces the impact of the seam 133 on waveguideperformance. The feed 130 for the waveguide is also incorporated intothe design of the PWB 134. However, the design would impact the entirethickness of the PWB 134, whereas the techniques described above onlyrequires the top layers for the feed design. Also, the edge of the PWB134 becomes a critical dimension since it would be necessary to maintainrelatively small tolerances to ensure proper mating with between thewaveguide and the feed and it is relatively difficult (and thusexpensive) using present state of the art manufacturing techniques tomaintain thickness variations of a multi-layer PWB to 10% or less.Moreover, this technique requires at least two parts. One part (e.g. thebottom half waveguide) can be incorporated into the support design asdescribe previously, but the other part (e.g. the top half waveguide)would need to be a separate part.

Referring now to FIGS. 7-7B, in which like elements are provided havinglike reference designations throughout the several views, an RFinterconnect is provided by connect a PWB 140 having first and secondground planes 140 a, 140 b with a coaxial PWB interconnection 142 havinga center conductor 144. The center conductor 144 is coupled to aconductor on the PWB 140. A series of plated through holes 146 providesa shield around the conductor 144. An electrical connection 150 is madethrough a pad 148 on the conductor 144 to a conductor 152 on the PWB140. In this manner, a RF connection is provided between the PWB 140 andthe coaxial PWB interconnection 142. A second PWB (nor visible in FIGS.7-7B) is coupled to the other end of the coaxial PWB interconnection142.

This approach has the advantage of simple assembly and the performanceof a coaxial connection. The disadvantage is in the significant addedcost of the PWB 142.

Referring now to FIGS. 8-11 in which like elements are provided havinglike reference designations throughout the several views, a sensorassembly 160 includes a housing 162 having a bottom surface 162 a and aplurality of side walls 164 which provide the housing having an interiorrecess region 163 defined by the bottom surface 162 a and side walls164. A shoulder region 166 projects from the bottom surface 162 a andthe inner surfaces 164 a of the sides 164. A connector 168 has a firstportion provided on an outside surface 164 b of one of the housing sidewalls 164 and a second portion on an inside portion of the housing sides164 a. Projecting from the inside portion of the housing sidewall 164 ais an electrical interface 170 (here shown as a plurality ofelectrically conductive pins 170). The electrical interface 170 allowselectrical connections to be made through the connector 168. Theconnector 168 provides a structure through which power, ground and CANsignals can be coupled through the side walls 164 to sensor electronicswhich will be described below.

Disposed in the housing 166 is an electrical shield 172 which has aperimeter region 172 a and a bottom surface 172 b which does not haveany openings (i.e. there are no holes on the “floor” of the shield 172)When the shield 172 is disposed in the housing 164, a surface of theshield perimeter region 172 a rests upon the housing shoulder surface166 a to thus support the shield 172 in the housing 164. The shield hasone opening 174 through which pins 170 project when the shield 172 isdisposed in the housing 164 the shield also has four openings 175 a-175d which align with four corresponding mounting holes 171 provided in thecorners of the shoulder region 166 of the housing 162 (only one mountinghole 171 being visible in FIG. 8).

A PWB frame 176 (also referred to herein as a “frame” or a “supportstructure”) has first and second opposing surfaces 176 a, 176 b. Theframe 176 is a medium or structure in which the PWBs for antennas andelectronics for the sensor 160 are disposed in an organized fashion. Thestructure 176 additionally provides a means for allowinginterconnections for power signals, digital signals (e.g. logicsignals), analog signals and RF signals. Significantly, the supportsstructure also integrates all of the antenna connections (i.e. transmitand receive antenna connections) in a single structure. In preferredembodiments, the frame 176 provides a support structure for all of theelectronics associated with the sensor module 160.

The support structure may be provided using a die-cast technique (e.g.to provide the support structure as a die-cast structure). The supportstructure may also be provided using any other casting or non-castingtechnique and may be provided from any suitable material. It should beappreciated of course that other techniques, including but not limitedto molding or injection molding techniques may also be used. For reasonswhich will become apparent from the description provided herein below,at least portions of the surface 176 b must be conductive. Thus, in thecase where the support structure is not provided from an electricallyconductive material, at least portions of the support structure must bemade conductive (e.g. by plating techniques, deposition techniques orusing any other technique well-know to those of ordinary skill in theart).

A digital/power supply printed wiring board (PWB) 180 is coupled to thefirst surface 176 a of the frame 176. Transmitter and receiver circuitboards 182, 184 (also sometimes referred to herein as transmitter andreceiver PWBs 182, 184) are disposed on the second surface 176 b of theframe 176.

The transmitter and received circuit boards 182, 184 are each providedhaving an antenna side 182 a, 184 a, respectively and a component side182 b, 184 b respectively. The antenna sides 182 a, 184 a eachcorrespond to sides of the circuit boards 182, 184 from which antennas(not visible in the FIGs.) provided on the circuit boards transmit andreceive RF signals. As will become apparent from the description hereinbelow, the supports structure allows all of the antenna connections(i.e. transmit and receive antenna connections) to be integrated into asingle structure. In one embodiment, the transmit and receive antennasmay be the same as or similar to the types described in application Ser.No. 11/323,960, filed on even date herewith, inventor Dennis Hunt andentitled “GENERATING EVENT SIGNALS IN A RADAR SYSTEM”; application Ser.No. 11/323,458, filed on even date herewith, inventors Dennis Hunt andW. Gordon Woodington and entitled “MULTICHANNEL PROCESSING OF SIGNALS INA RADAR SYSTEM” and in application Ser. No. 11/324,035, filed on evendate herewith, inventors Dennis Hunt and W. Gordon Woodington andentitled “VEHICLE RADAR SYSTEM HAVING MULTIPLE OPERATING MODES”.

A first side 180 a of the digital/power supply PWB 180 has digitalcircuit components disposed thereon while a second side 180 b of the PWB180 (i.e. the power supply side of the PWB 180) has power supplyelectronics disposed thereon. Thus, the power supply electronics are onthe same side of the PWB 180 as the shield 172. In this way, the shield172 prevents signals generated by the power supply electronics fromemanating through the housing 164 and interfering with the remainingelectronics of the sensor 160 or other electronic/electrical systems ofa vehicle in which the sensor 160 is disposed. The PWB 180 has a region181 which accepts the pins 170 to thus couple signals between theconnector 168 to the radar electronics mounted on the frame 176.

The first or digital circuit side of the PWB 180 a has disposed thereondigital circuit components including but not limited to a microprocessor184, a digital signal processor 186, power control circuitry 188 and aCAN transceiver 190. The PWB 180 also includes an interface (or connect)region 192 adapted to receive an interconnect circuit 194 (also referredto as a connector or a header). In particular, interface region 192includes a pair of alignment holes 195 having a size and shape adaptedto accept alignment pins 199 projecting from the interconnect circuit194. The interconnect circuit 194 provides electrical signal paths whichinterconnect circuits (power and digital circuits) on the PWB 180 tocircuits on particular portions of the transmitter and receiver circuitboards 182, 184. In the exemplary embodiment shown in FIG. 8, theinterconnect circuit 194 is provided as a header 194 and theinterconnect region 192 is provided as a plurality of openings 197 inthe PWB 180 which are adapted to accept pins 196 projecting from theheader 194 (the pins 196 can be most clearly seen in FIG. 10). The pinsmay be provided having any size and shape as long as the size and shapeof the pins 196 and openings 197 in the PWB 180 are selected such thatthe pins mate with the openings in such a manner so as to form areliable electrical connection between the pins and the PWB.

The header 194 also includes a pair of alignment structures 198 a, 198 bwhich are used to help properly align the header onto the supportstructure 176. In the exemplary embodiment shown in FIG. 8, thealignment structures 198 a, 198 b are provided as alignment posts 198 a,198 b and the support structure 176 is provided having a correspondingpair of recesses or openings (not visible) which accept the posts 198 a,198 b. With the alignment posts disposed in the openings, the header 192is properly aligned on the support structure 176 and pins 200 projectingfrom two opposing sides of the header 194 are aligned with openings 202provided in the support structure 176. The pins 200 are disposed throughthe support structure openings 202 such that the pins 200 contactelectrically conductive regions 204, 206 (FIG. 10) on the transmitterand receiver circuit boards 182, 184, respectively. The conductiveregions 204, 206 are also sometimes referred to herein as “contactregions” or “pads.”

As mentioned above, the support structure 176 can be provided using avariety of different manufacturing techniques. It should be appreciatedthat in the case where a molding technique is used to provide thesupport structure, the connector 194 can be molded as part of thesupport structure 176. This would eliminate the connector 194 as aseparate part. Also, it would be possible to use press-fit technology tocouple the connector to one or more of the circuit boards 180, 182, 184(this press-fit approach can be done regardless of the manufacturingtechnique used to provide the support structure 176). For example,instead of soldering connector pins 196 to the digital/power supplycircuit PWB 180, the connector pins 196 could be press fit intoreceptacles (e.g. holes) provided in the digital/power supply circuitPWB 180.

The support structure 176 includes a plurality of recess regions 210,212, 214, 216, 218. The size and shape of each recess region is selectedto accommodate a particular circuit on respective ones of the circuitboards 182, 184.

Frame 176 is provided having a pair of alignment structures 203 a, 203 b(FIG. 9) projecting from surface 176 b. In the exemplary embodiment ofFIGS. 8 and 9, the alignment structures are provided as alignment posts203 a, 203 b. The transmitter circuit 182 is provided having a pair ofholes 205 a, 205 b (FIG. 9) which accept the alignment posts when thetransmitter circuit board is disposed over the frame 176. Thetransmitter circuit board, may, for example, be provided as an LTTCcircuit board. In the view of FIG. 8, the transmitter circuit componentsare on the “down” side of the transmitter circuit board 182 (i.e. on theside of the board 182 facing surface 176 b of the frame 176). Thus, withthe transmitter circuit board 182 disposed over and properly aligned onthe frame 176, certain circuitry on the transmitter circuit board 182 isaligned with certain ones of the frame recesses 210, 212, 214.

In particular, a blockage detection circuit (not visible in the FIGs.)provided on the transmitter circuit board 182 is aligned over recess210, a transmitter circuit (not visible in the FIGs.) provided on thetransmitter circuit board 182 is aligned over recess 212 and an antennaelement/feed circuit (not visible in the FIGs.) provided on thetransmitter circuit board 182 is aligned over recess 214. When thetransmitter circuit board 182 is disposed over the frame 176, raisedportions or walls 219 of the frame 176 contact conductive portions ofthe transmitter circuit board 182. That is, the shape of the raisedportions 219 of the frame 176 mimics the position of conductive material(e.g. a ground plane) provided on the transmitter circuit board 182.Thus, once the circuit board is disposed on the support structure, therecess regions 210-214 act as cavities in which the respective blockagedetection circuit, transmitter circuit and antenna element/feed circuitoperate. Arranging circuits in separate cavities (e.g. arranging each ofthe blockage detection circuit, transmitter circuit and antennaelement/feed circuit) in a separate cavity serves to help isolatesignals (and in particular, RF signals) on each of the differentcircuits from each other.

Similarly, the frame 176 is provided having a plurality of alignmentstructures 230 a, 230 b, 230 c 230 d, 230 e projecting from framesurface 176 b. In the exemplary embodiment of FIGS. 8 and 9, thealignment structures are provided as alignment posts or detents 230a-230 e. The receiver circuit board 184 is disposed over the frame 176such that side 185 a contacts post 230 a, 230 b and that receivercircuit board side 185 b contacts post 230 c. The receiver circuitboard, may, for example, be provided as an LTTC circuit board. In theview of FIG. 8, the received components are on the “down” side of theboard 184 (i.e. on the side of the board facing surface 176 b of theframe 176). Thus, with the receiver circuit board 184 disposed over andproperly aligned on the frame 176, certain circuitry on the down side ofthe receiver circuit board 184 is aligned with certain ones of the framerecesses 216, 218.

In particular, a receiver and signal generation circuit (not visible inthe FIGs.) provided on the receiver circuit board is aligned over recess216 and an antenna element/feed circuit (not visible in the FIGs.) isaligned over recess 218. When the receiver circuit board 184 is disposedover the frame 176, raised portions (or walls) 232 of the frame contactconductive portions of the receiver circuit board 184. That is, theshape of the raised portions 232 of the frame 176 mimics (i.e. followsthe same path as) a conductor provided on the transmitter circuit board184. Thus, when the circuit board 184 is disposed over the frame, therecess regions act 216, 218 as cavities in which the receiver/signalgeneration portion of the receiver circuit board and the antennaelement/feed circuit of the receiver circuit board are disposed.Arranging circuits in separate cavities (e.g. arranging each of thereceiver/signal generation portion of the receiver circuit board and theantenna element/feed circuit) serves to help isolate signals on each ofthe different circuits from each other. Thus, the combination of theconductors (e.g. ground planes) on the circuit boards 182, 184 and thecavity arrangements help provide good isolation between circuits.

A waveguide transmission line 240 provided as an integral part of theframe 176 has a first port 240 a and a second port 240 b.

Referring briefly to FIGS. 10 and 11, cut away views of the waveguide240 are visible and it can be clearly seen that the support structure176 includes as an integral part thereof, at least a portion of thewaveguide transmission line 240 which couples RF signals between thetransmit and receive circuit boards 182, 184. As shown in the exemplaryembodiment of FIGS. 10 and 11, three sides of a rectangular transmissionline 240 are integrally formed in the support structure 176. A fourthwall of the waveguide transmission line 240, is provided by a conductor181 provided on the surface 180 a of the digital/power supply PWB 180(i.e. the digital circuit side of the PWB 180). The conductor 181 may bea conductive material disposed on a the surface 180 a of the PWB 180 orit may be a separate piece or material. It should also be appreciatedthat although conductor 181 is provided on the digital/power supply PWB,in other embodiments a fourth waveguide wall or other waveguide portionsnot integrally formed in the support structure may be disposed on orprovided as part of the transmitter or receiver circuit boards 182, 184(depending upon circuit configurations which may be different fordifferent applications). Thus, when the PWB 180 is disposed over thesupport structure 176, the conductor 181 on the PWB 180 forms the fourthwall of the waveguide transmission line 240.

When the transmitter and receiver circuit boards 182, 184 are properlyaligned and disposed on the frame 176, the waveguide transmission line240 has a first port 240 a disposed over a first waveguide couplingcircuit (or probe) 243 provided on the transmitter circuit board 182 anda second port 240 b disposed over a second waveguide coupling circuit(or probe) 245 provided on the receiver circuit board 184. The couplingcircuits 243, 245 couple signals from the respective waveguide ports 240a, 240 b to circuitry provided on the respective transmitter andreceiver circuit boards 182, 184. It should be appreciated that althoughthe coupling circuits 243, 245 are here shown provided as conductors onthe component sides of the circuit boards 182 b, 184 b which form patchelements, other types of waveguide coupling circuits, including but notlimited to pin-type probes, could also be used. Thus, the waveguidetransmission line 240 provides a signal path through which signals arecoupled between the transmitter and receiver circuit boards 182, 184.The waveguide transmission line 240 may be the same as or similar to thetype described in conjunction with FIGS. 1-4 above.

It should be understood that the waveguide may be provided having anyshape (e.g. circular or any other shape) and that the particular mannerin which the waveguide is integrally formed in the support structure andthe manner in which signals are coupled to and from the waveguide (e.g.use of pin probes vs. printed circuit probes) is selected to minimizethe number of separate components needed to form an operable RF signalpath between the transmit and receive circuit boards.

In one embodiment, the transmitter and receiver boards 182, 184 areconductively bonded to the support 176 using a compliant adhesive. Theadhesive can be applied in any and/or all locations along which asupport structure surface 176 b contacts the circuit boards 182, 184.

Referring again to FIGS. 8-11, it should be appreciated that thetransmit and receive circuit boards, 182, 184 can be coupled to theframe 176 using any one of a variety of different techniques. In oneparticular embodiment, a conductive epoxy is disposed on the frame 176in a pattern which mimics the ground plane on both the transmit andreceive printed circuit boards. In one particular embodiment, theconductive epoxy is disposed on walls 219, 232.

Due to constraints on the overall thickness of the sensor assembly, thecavities formed by placing the transmitter circuit board 182 over theframe recesses 210, 212, 214 are not very deep. Thus, prior to placingthe transmitter circuit board 182 over the frame 176, an RF absorbingmaterial 220 is disposed in the transmitter circuit cavity 212. Theabsorber 220 helps to absorb any stray RF signals emitted by thetransmitter circuit and thus helps reduce the amount of RF energy whichleaks from the transmitter cavity. This is desirable since leakagesignals can interfere with or reduce the effectiveness of the operationof other circuit in disposed in the frame 176 (including but not limitedto circuits both on and off the transmitter circuit board 182.

Similarly, prior to placing the receiver circuit board over the frame176, an RF absorbing material 250 is disposed in the receiver circuitcavity 212. The absorber 250 reduces the amount of RF signal which canleak from the receiver cavity 216. This is desirable since the leakagesignal can interfere with, or reduce, the effectiveness of the operationof other circuits in disposed in the frame 176 (including but notlimited to circuits both on and off the receiver circuit board 184.

The RF absorbing materials 220, 250 are also visible in FIGS. 10 and 11.In one embodiment, the absorbers 220, 250 attached to the cavity wallsusing a pressure sensitive adhesive.

Once the transmitter circuit board 182 is properly disposed on the frame176, the exposed surface 182 a of the transmitter circuit board 182 issubstantially aligned with a top surface of two raised portions 252 a,252 b (FIG. 9) which project from the frame surface 176 b. Thus, thesurface 176 b of the support structure corresponding to a top surface oftwo raised portions 252 a, 252 b, is provided having a height selectedto substantially match the height of the ground plane of the transmitantenna provided on the transmit antenna circuit board 182. By havingthe frame surface 176 b substantially matching the ground plane of thetransmit antenna, the ground plane of the transmit antenna iseffectively extended. It is desirable to extend the transmit antennaground plane since this improves the operating characteristics of thetransmit antenna.

Ideally, to provide a smooth electrical transition between the groundplane of the transmitter circuit board (i.e. the antenna ground plane)and the ground plane provided by the surface 176 b of the supportstructure 176, no gap should exist between the transmitter circuit boardground plane (i.e. the edge of the transmitter circuit board 182) andthe edge of the raised portions 252 a, 252 b. In practical systems,however, due to required manufacturing tolerances and imperfections, agap typically does exist in that region. Thus, to further improve thetransmit antenna performance, absorber material, 260 a, 260 b isdisposed over the gap between transmitter circuit board 182 and theframe surface 176 b.

In particular, the absorber 260 a, 260 b is disposed such that it coversat least a portion of the transmitter circuit board 182 and at leastportions of the raised frame regions 252 a, 252 b. The absorber 260 a,260 b thus covers any space (or gap) between the raised frame regions252 a, 252 b and the transmitter circuit board 182. This helps toprovide a smooth electrical transition from the substrate ground plane(i.e. the antenna ground plane) to the ground plane provided by thesurface 176 b of the support structure 176. The absorbers 260 a, 260 balso thus help to stabilize the side lobe levels on the certain antennabeams.

It should be appreciated that rather than using an absorber material tohelp provide a smooth electrical transition between the antenna groundplane and the ground plane provided by the surface 176 b, a conductivematerial could also be used. It should be further appreciated that sidesof the raised portions 252 a, 252 b distal from the transmitter circuitboard (i.e. sides 253) could be tapered such that a smooth physicaltransition exists between the top surfaces of the regions 252 a, 252 band other lower portions of the surface 176 b.

A radome 270 (FIG. 9) provided from a material which is substantiallytransparent to RF signals transmitted and received by the sensor 160 isdisposed over the upper or exposed sides 182 a, 184 a of the transmitterand received circuit boards. The radome can be attached to the housingany technique well known to those of ordinary skill in the art. In apreferred embodiment, the radome is welded to the housing via a laserwelding technique which provides a laser weld joint which connects theradome to the housing.

The radome 270 is provided having a breather vent 272. The breather vent272 allows moisture vapour to move in and out of the sensor assembly162. In particular, heat generated by the sensor assembly electronics(typically about 2.5 Watts) drives moisture and moisture vapour (e.g.condensation which may accumulate in the sensor) out of the unit throughthe breather vent 272. The moisture vent 272 thus helps preventsmoisture from saturating the antennas and other electronics provided aspart of the transmitter and received circuit boards 182, 184. Its isdesirable to remove moisture from the sensor assembly since moistureattenuates RF signals in certain frequency ranges. Such attenuationwould typically result in degradation in the operating performance ofthe sensor assembly 160.

Since the cost of manufacturing a unit which can be hermetically sealedis relatively high and thus cost prohibitive to large scalemanufacturing of the sensor assembly at a reasonable cost, the ideabehind using a moisture vent is to expose the sensor assembly 160 to atlease portions of the environment and to allow heat generated by thesensor assembly to drive out any moisture which may accumulate withinthe sensor while the sensor is not operating. That is, while the sensoris not operating, moisture (e.g. due to condensation) may accumulate inthe sensor. When the sensor is turned on (i.e. the sensor is operating),the unit generates an amount of heat sufficient to drive any accumulatedmoisture from the sensor. Also, the heat generated by the sensor whilethe sensor is operating prevents moisture from accumulating inside thesensor assembly 160 during sensor operation.

A breathable vent cover may be disposed over the vent 272 to prevent anydirt or any large particles (including large water particles fromentering the unit through the vent.

The vent 172 also prevents “oil canning” of the unit which may otherwiseoccur due to changes in temperature and/or pressure (e.g. pressurechanges due to changes in altitude).

The sensor assembly 160 may be assembled in the following manner. Thetransmitter circuit board 182 and the receiver circuit board 184 (alongwith absorbers 220, 250) are attached to the support structure 176. Asmentioned above, one technique for attaching the transmitter andreceiver circuit boards 182, 184 to the frame is to use conductiveepoxy. Next, the header is disposed on the frame 176 and the header pins200 are electrically connected to corresponding connection points (e.g.conductive pads) on the transmitter and receiver circuit boards 182,184. Such an electrical connection may be achieved, for example, bysoldering the pins 200 to conductive pads. With the header 192 and thetransmitter and receiver circuit boards 182, 184 coupled to the frame,the digital/power supply circuit board 180 is disposed on the frame 176such that the header pins 199 mate with holes and pads provided in theinterface region 191 of the digital/power supply circuit board 180. Theheader pins 196 are electrically coupled to corresponding electricalconnection points on the digital/power supply circuit board 180. Such anelectrical connection may be achieved, for example, by soldering thepins 196 to the connection points.

Once attached to the support structure 176, the digital/power supplycircuit board, the transmitter circuit board 182 and the receivercircuit board 184 along with absorbers 220, 250 (and optionally absorber260) provide a so-called radar electronics module 251 (FIG. 9). In thecase where absorber 260 is used, it is desirable to attach the receivercircuit board 184 to the frame 176 prior to attaching absorber 260 toensure proper positioning of the absorber 260.

The shield 172 and radar electronics module 251 are then disposed in andsecured to the housing 164. As shown in FIG. 8, the shield 172 and radarelectronics module are secured to the housing via screws 300 whichfasten the shield 172 and radar electronics module to the housing 162(FIG. 8). It should be appreciated that other fastening techniques mayalso be used to fasten the shield 172 and radar electronics module 251to the housing 162. Once the shield and the radar electronics module aresecured in the housing 162, the radome 270 is secured to the housing164. As mentioned above, the radome may be secured to the housing 164 bylaser welding the radome to the housing 164.

It should be appreciated that other processes may also be used toassemble the sensor assembly. It should also be appreciated that thecircuit boards 180, 182, 184 may be manufactured from any suitablematerial.

It should also be appreciated that since the base 172 b of the shield172 does not have any openings provided therein and since thetransmitter and receiver circuit boards 182, 184 also do not have anyopenings therein, once the shield 172 covers the radar electronicsmodule 251, a closed box is formed. This closed box is then furtherenclosed in a second box formed by housing 162 and cover 270. Thus, thesensor 160 is packaged as a box-within-a-box. This box-within-a-boxpackaging approach further protects the sensor module electronics fromenvironmental conditions.

It should be appreciated that the sensor 160 and circuit boards 180, 182and 184 may be the same as or similar to the types described inapplication Ser. No. 11/323,960, filed on even date herewith, inventorDennis Hunt and entitled “GENERATING EVENT SIGNALS IN A RADAR SYSTEM”;application Ser. No. 11/323,458, filed on even date herewith, inventorsDennis Hunt and W. Gordon Woodington and entitled “MULTICHANNELPROCESSING OF SIGNALS IN A RADAR SYSTEM” and in application Ser. No.11/324,035, filed on even date herewith, inventors Dennis Hunt and W.Gordon Woodington and entitled “VEHICLE RADAR SYSTEM HAVING MULTIPLEOPERATING MODES”.

Having described the preferred embodiments of the invention, it will nowbecome apparent to one of ordinary skill in the art that otherembodiments incorporating their concepts may be used. It is felttherefore that these embodiments should not be limited to disclosedembodiments but rather should be limited only by the spirit and scope ofthe appended claims. All publications and references cited herein areexpressly incorporated herein by reference in their entirety.

1. A sensor assembly comprising: a housing having a bottom surface and aplurality of side walls which define an interior recess region, saidhousing having a shoulder region projecting from the bottom surface andthe side walls around a perimeter of the interior recess region; anelectrical interface projecting from the a top surface of the shoulderregion; an electrical shield disposed in the recess region of saidhousing, said electrical shield having a size and shape selected suchthat when said electrical shield is disposed in the housing, a firstsurface of a perimeter region of said electrical shield rests upon a topsurface of the shoulder region of said housing to support saidelectrical shield in said housing and a second surface of the perimeterregion of said electrical shield is in proximity to a side surface ofthe shoulder region and wherein said electrical shield is providedhaving one opening in the surface of the perimeter region through whichat least a portion of said electrical interface projects when saidelectrical shield is disposed in said housing and wherein a bottomsurface of said electrical shield does not have any openings providedtherein; a radar electronics module disposed over said electrical shieldand electrically coupled to said electrical interface; a radome disposedover said radar electronics module and coupled to the sidewalls of saidhousing; and a breather vent disposed in said radome.
 2. The sensorassembly of claim 1 wherein said radar electronics module comprises: adigital/power supply printed wiring board (PWB); a transmitter circuithaving a transmit antenna; a receiver circuit having a receive antenna;a PWB frame having first and second opposing surfaces, said PWB framedisposed over said electrical shield within the recess region of saidhousing, with a first one of said first and second opposing surfaces ofsaid PWB frame configured to hold said digital/power PWB and a secondone of said first and second opposing surfaces of said PWB frameconfigured to hold said transmitter and receiver circuits and said PWBframe also configured to provide interconnections for power signals,digital signals, analog signals and RF signals between saiddigital/power PWB and said transmitter and receiver circuits.
 3. Thesensor assembly of claim 2 wherein said PWB frame includes a firstplurality of recess regions having a size and shape selected toaccommodate particular circuits on said transmitter circuit and said PWBframe includes a second plurality of recess regions having a size andshape selected to accommodate particular circuits on said receivercircuit.
 4. The sensor assembly of claim 3 further comprising an RFabsorbing material disposed in at least one of the first plurality ofrecess regions to absorb RF signals emitted by said transmitter circuit.5. The sensor assembly of claim 2 further comprising an absorbermaterial disposed over a gap between said transmitter circuit and asurface of said PWB frame, said absorber disposed such that it covers atleast a portion of said transmitter circuit and at least a portion saidPWB frame.
 6. The sensor assembly of claim 2 further comprising: aconnector having a first portion provided on an outside surface of oneof the housing side walls and a second portion on an inside portion ofthe housing side walls, said connector electrically coupled to saidelectrical interface to allow electrical connections to be made throughthe connector such that the connector provides a structure through whichpower, ground and car area network (CAN) signals can be coupled throughthe side walls of said housing to said radar electronics module.
 7. Thesensor assembly of claim 2 wherein said PWB frame includes a portion ofa waveguide which couples of RF signals to the transmit and receivecircuits and wherein a surface of said digital/power supply PWB forms awall of the waveguide.
 8. The sensor assembly of claim 1 wherein saidbreather vent allows moisture vapour to move in and out of the sensorassembly.
 9. The sensor assembly of claim 8 wherein said digital/powersupply PWB has digital circuit components disposed on a first sidethereof and power supply electronics disposed on a second side thereofsuch that the power supply electronics are on the same side of the PWBas said electrical shield such that said electrical shield preventssignals generated by the power supply electronics from emanating throughsaid housing.
 10. The sensor assembly of claim 8 wherein saiddigital/power supply PWB has a region which accepts said electricallyconductive pins to couple signals between said connector and the radarelectronics module disposed on said PWB frame.
 11. The sensor assemblyof claim 10 further comprising: a blockage detection circuit disposed onthe transmitter circuit board and aligned over a first recess; atransmitter circuit provided on the transmitter circuit board andaligned over a second recess; and an antenna element/feed circuitprovided on the transmitter circuit board and aligned over a thirdrecess.
 12. The sensor assembly of claim 11 wherein when the transmittercircuit board is disposed over the PWB frame, raised portions or wallsof the frame contact conductive portions of the transmitter circuitboard.
 13. The sensor assembly of claim 12 wherein the shape of theraised portions of said PWB frame mimics a conductor provided on saidtransmitter circuit such that when said receiver circuit is disposedover said PWB frame, raised portions of said PWB frame contactconductive portions of said receiver circuit and when said transmittercircuit is disposed over said PWB frame, recess regions in said PWBframe as cavities in which the receiver/signal generation portion of thereceiver circuit board and the antenna element/feed circuit of thereceiver circuit board are disposed and wherein arranging each of thereceiver/signal generation portion of the receiver circuit board and theantenna element/feed circuit in separate cavities serves to help isolatesignals on each of the different circuits from each other.
 14. Thesensor assembly of claim 1 wherein said electrical interface is providedas a plurality of electrically conductive pins.
 15. A method forassembling a sensor assembly comprising: (a) attaching a transmittercircuit board, a receiver circuit board, and absorbers to a PWB frame;(b) disposing a header on the PWB frame and electrically coupling headerpins to corresponding connection points on the transmitter and receivercircuit boards; (c) with the header and the transmitter and receivercircuit boards coupled to the frame, disposing the digital/power supplycircuit board on the frame such that the header pins mate with holes andpads provided in an interface region of a digital/power supply circuitboard; (d) electrically coupling header pins to corresponding electricalconnection points on the digital/power supply circuit board; (e)securing a shield and a radar electronics module to a housing; (f) oncethe shield and the radar electronics module are secured in the housing,securing a radome to the housing.
 16. The method of claim 15 whereinattaching the transmitter and receiver circuit boards to the PWB framecomprises using conductive epoxy.
 17. The method of claim 16 whereinelectrically coupling header pins to corresponding connection points onthe transmitter and receiver circuit boards comprises soldering the pinsto conductive pads on the transmitter and receiver circuit boards. 18.The method of claim 17 wherein electrically coupling header pins tocorresponding electrical connection points on the digital/power supplycircuit board comprises soldering the pins to the connection points. 19.The method of claim 18 wherein securing the shield and radar electronicsmodule to the housing comprises fastening the shield and radarelectronics module to the housing via screws.
 20. The method of claim 15wherein securing the radome to the housing comprises welding the radometo said housing.